A power converter for an electric locomotive supplied with power from an AC overhead wire includes a main power converter which controls an electric driving motor and an auxiliary power converter (auxiliary power supply) for supplying power to a compressor and a cooling blower in the locomotive.
The main power converter and the auxiliary power converter are supplied with AC power from individual secondary windings of a main transformer which receives power from the AC overhead wire, to convert the AC power to DC power by individual converters (AC/DC converting circuits).
In the main power converter, a variable voltage, variable frequency inverter is connected to a stage following the converter.
In the auxiliary power converter, a constant voltage, constant frequency inverter (APU: auxiliary power unit) is connected to a stage following the converter.
The above-described conventional auxiliary power converter is provided with a three-phase LC resonant filter (low-pass filter) in order to decrease harmonic components of a three-phase AC output to obtain an approximately sinusoidal waveform.
In case of an electric locomotive, a reactor L of the LC resonant filter is required to have a capacity of approximately 380 V, 50 Hz, and 230 kVA when an inductance is approximately 380 μH.
Therefore, the reactor L becomes significantly large in weight of 400 kg or heavier, which causes an increase in the size of the power converter including the APU circuit.